The present invention generally relates to an indicator system that can detect the depletion of a variety of chemicals. More particularly, the present invention is directed to a visual indicator system that can be employed in use-dependent products to detect either the exhaustion or depletion of a chemical included therein. For example, the color indicator system of the present invention can be employed in food service wipers to detect the depletion of chemicals, such as anti-microbial agents.
A use-dependent device or product is normally considered to be a product that becomes less effective over time. The decline in effectiveness of a particular use-dependent product can be caused by a variety of factors. One such factor that is significant in many applications is the depletion of an active chemical incorporated within the product. For example, wipers, such as those used in medical and food service applications, may contain an anti-microbial agent that is released during wiping to create a solution for disinfecting the surface being wiped. The anti-microbial agent helps prevent potentially harmful microorganism contamination when wiping a particular surface.
Typically, a user of a use-dependent product will want to know when the chemical within the product has been exhausted so that the user can discard the depleted product and begin to use a new one. If no such method is available for determining when the chemical has been exhausted, a user will unknowingly continue to use a product that has been rendered ineffective. For example, in the food service industry, it would be important to determine when an anti-microbial agent of a wiper has been exhausted so that it will not continue to be used thereafter.
In the past, various systems have been developed to indicate variables such as lapses in time, the presence of chemicals, or the absence of chemicals. For example, time indicators, such as disclosed in U.S. Pat. No. 5,699,326 to Haas et al., have been developed to communicate a lapse in time through the use of a visual change in color. Other time indicators are disclosed in U.S. Pat. No. 5,317,987 to Muller et al. and U.S. Pat. No. 4,248,597 to McNeely. In addition to indicators that reveal a lapse in time, indicator systems that detect the presence or absence of a chemical have also been developed. For example, U.S. Pat. No. 4,205,043 to Esch et al. discloses a system that employs a color-sensitive gas to detect the presence of chlorine dioxide.
Besides the above indicator systems, other indicators have been developed to detect the absence of a chemical within a use-dependent product, such as a sanitizing or anti-microbial wiper. For example, an anti-microbial wiper has been marketed by Pal International Inc. of England under the name WIPEX. According to the sales literature, this wiper contains an anti-microbial agent to sanitize various surfaces. In addition, the wipers include indicator stripes that are stated to fade gradually as the disinfectants are depleted. It is believed that U.S. Pat. No. 4,311,479 to Fenn et al. is related to this particular anti-microbial cloth. This indicator system, however undesirably reduces the hydrophilic nature of the wiper.
As such, a need currently exists for a more effective indicator system for use in use-dependent products. In particular, a need exists for an indicator system that can be incorporated into articles containing chemicals such as anti-microbial agents, without having a substantial adverse effect on the properties of the chemicals. Examples of such articles include anti-microbial and/or sanitizing wipers.
Accordingly, an object of the present invention is to provide an improved use-dependent indicator system.
It is another object of the present invention to provide an indicator system that can signal the depletion of a chemical incorporated within an absorbent article.
Still another object of the present invention is to provide an indicator system that can signal the depletion of a chemical incorporated within an absorbent article without having a substantial adverse affect on the properties of the article that are provided by the chemical.
Yet another object of the present invention is to provide an indicator system containing at least one dye component.
Another object of the present invention is to provide an indicator system containing reactive and/or non-reactive dyes.
It is another object of the present invention to provide an indicator system containing a dye component(s) that can dissolve faster than an active chemical such that the dissolution of the dye can signal the impending exhaustion of the active chemical.
Still another object of the present invention is to provide an indicator system that contains a polymer mixture.
Yet another object of the present invention is to provide an indicator system that contains a polymer mixture that can retain its strength and adhesion properties after being applied to a web, and thereafter creped and cured.
Another object of the present invention is to provide an article in which less than 60% of one side of a cloth-like web is printed with the indicator system.
It is another object of the present invention to provide an indicator system that can provide sufficient control over the dissolution rates of the dye component(s) such that the system can effectively signal the depletion of the active chemical.
These and other objects of the present invention are achieved by providing an absorbent article such as a nonwoven web to which an indicator system of the present invention can be applied. An indicator system of the present invention generally includes at least one dye component and a polymer mixture.
In accordance with the present invention, any material commonly used in the art to manufacture cloths, such as wipers, can be used as the base web. In particular, a base web of the present invention is typically made from a nonwoven polymeric or paper-based web. More particularly, a base web of the present invention can be made from pulp fibers, synthetic fibers, thermomechanical pulp, or mixtures thereof such that the web has cloth-like properties. For instance, the base web can be made from softwood pulp fibers, such as Northern softwood kraft fibers, redwood fibers and pine fibers. Moreover, the base web can also include staple fibers, such as polyolefin fibers, polyester fibers, nylon fibers, polyvinyl acetate fibers, cotton fibers, rayon fibers, non-woody plant fibers, and mixtures thereof. In one embodiment, a base web of the present invention can also be webs that have been subjected to post treatment process such as hydroentanglement. In addition, the web can be a co-form material such as disclosed in U.S. Pat. No. 4,100,324 to Anderson et al. and U.S. Pat. No. 5,350,624 to Georger et al., which are incorporated herein in their entireties by reference thereto.
After forming the base web, an indicator system of the present invention can be applied. In general, the indicator system contains at least one dye component and a polymer mixture. Depending on the application, a single dye or combination of dyes can be used. In one embodiment, the indicator system includes a non-reactive dye, such as a foodstuff dye, that can dissolve out of an article to which it is applied. In other embodiments, the indicator system can include a reactive dye, such as a cationic dye, combined with a non-reactive dye. A reactive dye is typically permanent and will not dissolve out of the article. The combination of dyes selected generally depends on whether the article is desired to retain a color after the active chemical therein has been exhausted.
An absorbent article of the present invention also includes an active chemical, which is used for a variety of reasons. The active chemical can be applied to the article separately, or as part of an indicator system of the present invention. In one embodiment, the active chemical is incorporated within the indicator system as an anti-microbial agent used in wipers. In general, the active chemical within an article will become depleted and will eventually be exhausted after repeated use.
In certain embodiments, the indicator of the present invention will be incorporated into a wiper capable of providing liquid anti-microbial solution after numerous rinse cycles. Such a wiper will generally include a controlled release anti-microbial formulation comprising an anti-microbial agent, which formulation is adhered to an absorbent, cloth-like web which retains liquid after each rinse cycle. The combination of the anti-microbial formulation and the retained liquid in the wiper is adapted so that the formulation releases sufficient anti-microbial agent into the retained liquid after each of at least five normal rinse cycles so that the retained liquid is an anti-microbial solution.
In certain embodiments, the anti-microbial formulation can include an anti-microbial agent encapsulated in, adsorbed to, or as a part of a particle or microcapsule. In certain embodiments, the anti-microbial formulation may be in the form of an anti-microbial agent that is coated by or enclosed in a polymer coating.
As stated, an indicator system of the present invention can also contain a polymer mixture. In some embodiments, a polymer mixture of the present invention can xe2x80x9cbloomxe2x80x9d or swell in water. In general, a water-swellable polymer mixture of the present invention can contain a variety of components, such as a polymer. For instance, in one embodiment, the polymer mixture can comprise a polymer that is itself water-swellable. Any such water-swellable polymer, such as adhesives, are suitable for use in the present invention. Examples of adhesives that are suitable for use in the present invention include acrylates, styrene butadiene, vinyl chlorides, methacrylates, acrylics (such as carboxylated acrylics), and vinyl acetates (such as self cross-linking ethyl vinyl acetate, hydrolyzed polyvinyl acetate, or non-cross-linking ethyl vinyl acetate). In certain embodiments, the adhesive is made from carboxylated acrylics.
In certain embodiments of the present invention, the polymer mixture can comprise polymers that can become cross-linked. The use of cross-linked polymers, such as latex adhesives, can facilitate control of the dissolution rate of the dye component(s) and/or other chemicals. Specifically, increasing the amount of cross-linking in the adhesive results in less swelling, which in turn, can result in a slower release of the dye components and/or other chemicals into the liquid.
In accordance with the present invention, other various components can also be added as part of the polymer mixture as desired. For example, plasticizers, such as glucose triacetate, can be added to aid in the migration of the active chemical, such as an anti-microbial agent, to the polymer surface. In addition to plasticizers, cross-linking agents, catalysts, plasticizers, thickeners, defoamers, water, and the like, can also be added to a polymer mixture of the present invention. Furthermore, chemicals such as stabilizers, viscosity modifiers, composite particles, or surfactants, can be added as well.
Once an indicator system has been formed in accordance with the present invention, it can then be applied to the base web. Generally, an indicator system of the present invention can be applied to the base web as a chemical formulation by any commonly used method of application, including, but not limited to, print, print crepe, spray, blade, saturant, coating, droplet throw, and foam application methods. For instance, a system of the present invention can be applied as a saturant system, such as disclosed in U.S. Pat. No. 5,486,381 to Cleveland et al., which is incorporated herein in its entirety by reference thereto. Moreover, in another embodiment, the formulation may be printed onto one or both sides of the base web. In some embodiments, the indicator system can also be printed onto the base web as a chemical formulation in a preselected pattern.
The preselected pattern used to apply the indicator system formulation can be, in one embodiment, a reticular interconnected design. Alternatively, the preselected pattern can comprise a succession of discrete shapes, such as dots. In a further alternative embodiment of the present invention, the preselected pattern can be a combination of a reticular interconnected design and a succession of discrete shapes.
The indicator system applied to the base web can generally be applied in a preselected pattern that covers less than 100%, and more particularly from about 10% to about 60% of the surface area of each side of the web. For instance, in one embodiment, the indicator system can be applied as a stripe or other shape to at least one side of the base web.
The indicator system can also be applied to each side of the base web in an amount of from about 2% to about 8% by weight. Once applied, the indicator system can penetrate the base web in an amount from about 10% to about 60% of the total thickness of the web.
In some embodiments, after applying the indicator system to the base web, the web can then be creped to increase the softness, absorbency, and bulk of the web. Depending on the application, one or both sides of the web can be creped. Furthermore, the base web can be dried and cured after applying the indicator system. Curing can increase the strength of the base web, as well as aid in controlling the dissolution rate of the dye component(s) and/or other chemicals. In particular, controlling the degree of polymer curing can, in one embodiment, provide further control over the amount of swelling, which can, in turn, provide control over the dissolution rate of the dye component(s) and/or other chemicals.
In general, an indicator system of the present invention can include various mechanisms, such as a polymer mixture, curing methods, application methods, etc. to control the rate of dissolution of the dye component(s) and/or active chemical. By controlling the rate of dissolution in this manner, the indicator system can signal the complete exhaustion or the gradual depletion of the active chemical. In particular, the rate that a dye component dissolves out of an article can be controlled in a manner such that it dissolves from the article just prior to the active chemical. Therefore, due to a loss in dye, the article will lose or change color. Such a change or loss in color signals to a user the impending or complete exhaustion of the active chemical therein.
Other objects, features and aspects of the present invention are discussed in greater detail below.